WASHINGTON—Addressing the nation’s finances at a major economic conference Friday, Federal Reserve chairman Ben Bernanke acknowledged that for the past three years the United States has been scraping by on the revenue generated by the 2009 sci-fi blockbuster Avatar. “By circulating $2.8 billion through the economy in gross box-office receipts alone, the cash from Avatar has been the only thing keeping America’s head above water,” said a solemn-faced Bernanke, adding that when money from the theatrical release ran dry, DVD sales had been able to pick up just enough slack to keep the United States solvent for another year. “We had hoped the Avatar money would see us through the end of 2012, but at this point we’ve blown through all the revenue from toys, clothing, video games, and book tie-ins, and it appears we are now headed over the fiscal cliff.” With a sequel not expected until 2015, Bernanke called for an emergency rerelease of the film “in IMAX 3-D with bonus scenes” in order to prevent the United States from defaulting on overseas loans.